1. Field of the Invention
This invention relates generally to a mode-change mechanism for tape recorders of the type in which the mode of operation is changed in response to intermittent turning of a partially toothless gear, and the invention is more particularly directed to a mode-change mechanism of such type suited for use in auto/reverse tape recorders.
2. Description of the Prior Art
A mode-change mechanism for a tape recorder is already known in which a driving bar is mounted for reciprocating movements between positions corresponding to a record/playback mode and a stop mode, respectively, a partially toothless gear is intermittently rotatable by a driving gear for moving the driving bar between the mentioned mode selecting positions thereof, locking means are provided for locking the partially toothless gear in an immobile position in which a toothless portion of its periphery faces the driving gear, and urging means, such as a spring, are provided for imparting an initial torque to the partially toothless gear upon release of the locking means, whereupon the partially toothless gear meshes with the driving gear so as to be intermittently rotated by the latter.
An auto-reverse tape recorder is also already known in which a partially toothless gear is intermittently rotated so as to move a change-over bar between positions thereof corresponding to a forward tape running mode and a reverse tape running mode, respectively.
An auto-reverse tape recorder is also known in which a motor rotates a driving gear which continuously drives first and second intermediate gears for intermittently rotating first and second partially toothless gears, respectively, and the intermittently rotated first and second partially toothless gears effect the necessary movements of a driving bar and a change-over bar, respectively, for selecting the record/playback mode or stop mode and for selecting the forward tape running mode or reverse tape running mode, respectively.
In the above described mode-change mechanisms in which a driving bar is displaced by the intermittent rotation of a partially toothless gear, if the release of the locking means for holding the partially toothless gear in an immobile position is actuated by a solenoid or the like, the change-over between the record/playback mode and the stop mode can be effected in response to the manipulation of a so-called "feather touch" button, which is a desirable operating characteristic. However, in the described mode-change mechanisms, the partially toothless gear must be surely meshed with the respective driving gear as soon as the locking means is disengaged or released, and a mechanism including springs and the like is provided exclusively for the purpose of effecting such initial meshing engagement of the partially toothless gear with the respective driving gear. As a result of the foregoing, the number of parts and the steps required for the assembly of the mode-change mechanism are undesirably increased with a consequent rise in the complexity and cost of production. Further, difficulties are encountered in making compact the mechanism by which the partially toothless gear is initially urged into meshing engagement with the respective driving gear, with the result that desirable miniaturizing of the tape recorders provided with such mode-change mechanisms is prevented.
Moreover, the above described known mode-change mechanisms are susceptible to malfunctions upon change-over from the record or playback mode to a fast-forward or rewind mode. More particularly, in a tape recorder having a mode-change mechanism in which the driving bar is mechanically moved to a forward or record/playback mode position in response to actuation of a record/playback button, and the driving bar is moved backward to a stop mode position upon the actuation of a fast-forward/rewind button, if the movements of the driving bar in both the forward and backward directions occur in response to the driving of the partially toothless gear by the respective driving gear, the driving bar is only gradually accelerated during its movement in the backward direction as the partially toothless gear is rotated by the driving gear. Thus, a substantially instantaneous complete change-over from the playback or record mode to the fast-forward or rewind mode is not attained. Therefore, a pinch roller may still be pressed against a respective capstan at a time when the fast-forward or rewind mode is otherwise established with the result that the magnetic tape will be damaged. Further, by reason of the relatively slow backward movement of the driving bar upon actuation of the fast-forward/rewind button, a gear train provided for effecting rotation of a reel base at a speed characteristic of the playback or record mode may be engaged or driven simultaneously with a gear train provided for rotating the same reel base at a speed characteristic of the fast-forward or rewind mode, thereby causing either damage to the mechanism or otherwise interfering with the desired operation of the tape recorder.
Moreover, in the above described mode-change mechanism for a tape recorder in which the driving bar for changing-over between the record/playback mode and the stop mode and the change-over bar for changing between the forward and reverse tape running modes are driven by first and second partially toothless gears, respectively, and first and second intermediate gears are independently associated with the first and second partially toothless gears, respectively, so as to provide for the independent intermittent driving of the latter, it is apparent that the number of parts required for the mode-change mechanism is increased and the construction thereof is complicated. As a result of the foregoing, it is difficult to miniaturize a tape recorder embodying such mode-change mechanism.